Authors:Tack-Jin Kim, Yong-Kwang Jeong, Jun-Gill Kang, Yongju Jung, Do-Hee Ahn, and Han-Soo Lee
The spontaneous reduction of Eu3+ to Eu2+ was examined when EuCl3 was added into a pyroprocessing media of LiCl molten salt at 923 K. The amount of Eu2+ was calculated by measuring the total charge consumed to oxidize Eu2+ ions to Eu3+ ions. The concentration ratio of Eu2+ to Eu3+ was estimated to be about 0.40 in the media. In addition, it is confirmed that the reduction of Eu3+ to Eu2+ is caused by the oxidation power of Cl− to Cl2. The coexistence of Eu3+ and Eu2+ in the LiCl molten salt system was examined by UV–Visible and luminescence spectroscopy. The molar absorptivities of Eu3+ and Eu2+, calculated from UV–Visible absorption spectra, were 423 and 1954 M−1 cm−1, respectively.
Authors:Tack-Jin Kim, Yongju Jung, Joon-Bo Shim, Si-Hyung Kim, Seungwoo Paek, Kwang-Rak Kim, Do-Hee Ahn, and Hansoo Lee
In order to enhance the efficiency of pyrochemical technology, especially electrorefining process, physicochemical data of
trivalent uranium in LiCl–KCl eutectic at 773 K were measured, including molar absorptivity, formal potential and diffusion
coefficient of U3+ ions. The molar absorptivities of U3+ were determined to be 765 ± 48 and 686 ± 39 M−1 cm−1 at 465 and 550 nm, respectively. The formal potential of U3+/U4+ redox couple and diffusion coefficient of U3+ ions were measured to be −0.308 V vs. Ag/Ag+ and 8.7 × 10−6 M−1 cm−1, respectively. To elucidate the chemical behavior of U3+ ions under the existence of oxide ions, U3+ ions were reacted with oxides ions in situ produced at the LiCl–KCl media. Surprisingly, it was revealed from XRD patterns
that UO2 was formed from the reaction between U3+ ions and O2− ions with the molar ratio of 1:1.